This invention relates to an image output apparatus such as a printer connected to a host computer or the like, to a method of controlling the apparatus and to a storage medium for implementing this control method.
In the prior art, an image output apparatus, e.g., a printer such as a well-known laser printer, is connected to a host computer using a standard interface cable and includes a controller for interpreting an image signal described in page description language (PDL) entered from the host computer and for expanding the image signal into bitmap data, and an engine for converting the bitmap data expanded by the controller to a video signal and for printing the video signal on printing paper using an electrophotographic process.
The controller instructs the engine to start printing when the creation of one page of page data has been completed or when the expansion of one page of bitmap data has been completed. Upon receiving the command to print, the engine rotates an accompanying rotatable polygon mirror and transports the printing paper at the moment the polygon mirror has attained the prescribed rotational speed.
Modern printers are required to print at higher speeds. What is sought in particular is reduced processing time from the moment printing starts at the host computer to the moment the first page is discharged from the printer. This processing time is referred to as xe2x80x9cfirst-page discharge timexe2x80x9d.
There is also great demand for high image quality. To meet this demand, printers having multiple resolutions (600 dpi, 1200 dpi, etc.) are available. A shorter first-page discharge time is required in these multiple-resolution printers as well.
An alternative method of shortening first-page discharge time is to transport the printing paper up to a point just short of the printing position in advance of printing. Such a function is referred to as a xe2x80x9cpreliminary-feed functionxe2x80x9d. A printer having the preliminary-feed function is required to have an even shorter first-page discharge time.
According to the prior art, however, the polygon mirror is caused to rotate after the printer engine receives the print start command. As a consequence, it takes time for the polygon mirror to attain the stipulated rotational speed. In particular, as resolution rises and printing speed increases, there is greater need to rotate the polygon mirror at higher speed and, hence, it takes longer for the mirror to attain the stipulated rotational speed.
Accordingly, an object of the present invention is to provide an image output apparatus and method of controlling the same, wherein by causing the polygon mirror to rotate before the engine receives the print start signal, the first-page discharge time can be shortened even if printing is performed at a high resolution or high printing speed.
According to the present invention, the foregoing object is attained by providing an image output apparatus comprising: an image-information development unit for converting one page of page data to a video signal after print information has been analyzed and the one page of page data created; an image formation unit for transporting a print medium in sync with the video signal from the image-information expansion unit and forming an image on the print medium through an electrophotographic process by causing scanning of a beam, which has been modulated by the video signal, by a rotatable polygon mirror; and polygon-mirror rotation command means for causing the polygon mirror to rotate when creation of the page data starts.
The apparatus preferably further comprises: stopping means for stopping the rotating polygon mirror; first detection means for detecting whether a fixed period of time has elapsed from issuance of the polygon-mirror rotation command; and second detection means for detecting whether processing for transporting the print medium is being executed; wherein the rotating polygon mirror is stopped by the stopping means if the fixed period of time has elapsed from start of rotation of the polygon mirror and, moreover, processing for transporting the print medium is not being executed.
The apparatus preferably further comprises third detection means for detecting whether the print medium is being transported, wherein the polygon mirror is not rotated by the polygon-mirror command rotation means if the print medium is being transported.
The apparatus preferably further comprises fourth detection means for detecting whether created page data exists, wherein the polygon mirror is not rotated by the polygon-mirror rotation command means if at least one page of the page data exists.
The apparatus preferably further comprises stopping means for stopping the rotating polygon mirror; changing means for changing resolution of an image formed by said image forming means; and fifth detection means for detecting whether the resolution of the engine has been changed; wherein the rotating polygon mirror is stopped by the stopping means if the resolution of the engine is changed.
The apparatus preferably further comprises means for performing preliminary feed to transport the print medium in advance to a stage prior to printing when an image is printed on the print medium based upon image information that has been entered from an information processing unit, wherein the preliminary feed is not performed if resolution of the engine is changed by the changing means.
In a preferred embodiment, the changing means changes transport speed of the engine.
The apparatus preferably further comprises determination means for determining whether the page data is data accompanied by formation of an image by the image formation means, wherein if the determination means has determined that the page data is accompanied by formation of an image, the polygon-mirror rotation command means starts rotation of the polygon mirror when the page data starts to be created.